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Introduction

There are a variety of great embedded linux systems on the market today which enable quickly and easily programming hardware. Some, like the VEXPro Arm9 Microcontroller support an entire electro-mechanical robotics platform. Others, like the Chumby alarm clock or WRT54-class routers provide just an inexpensive linux controller. This class of device typically supports USB and wifi, has USB drivers for webcam and USB-serial dongles, is physically small, and consumes under 10 watts of electrical power. This makes them expandable and interesting for use on smaller robots, especially when vision is desired.

Using the rosserial_embeddedlinux package, you can use ROS directly with the these systems. rosserial provides a ROS communication protocol that works over your embedded linux system's serial UART, or its wifi or network connection. It allows your embedded linux system to run linux processes that are full fledged ROS nodes that can directly publish and subscribe to ROS topics, advertise services and request services, publish TF transforms, and get the ROS system time over any of the supported connection types.

There are three environments you'll have to deal with when using an embedded linux system: ROS, the embedded system development environment, and the embedded system itself. These are depicted below.

Rosserial_python presents the embedded linux application(s) as a ROS node(s), and proxies messages between embedded linux system and the rest of ROS.

The rosserial_embeddedlinux package supports the following major connection types and capabilities:

• TCP/IP or serial connection between ROS system and embedded linux system supports wifi, wired ethernet, USB-serial dongle, wired serial, etc.
• TCP/IP connection supports reconnect after disconnect (e.g. in case robot wanders out of range of wifi, or program on robot is restarted).
• TCP/IP connection supports multiple connections from processes on embedded linux systems. This supports both multiple processes on one robot (e.g. a vision process and a robot motion process), and multiple robots (or both).

Purpose of Package

This package contains embedded-linux-specific extensions required to run rosserial on a small embedded linux system such as the VEXPro controller, Chumby alarm clock, WRT54GL router, Raspberry Pi, or many similar devices. It is meant to demonstrate how easy it is to integrate custom hardware and cheap sensors including USB cameras into your ROS project using an embedded linux system. The Tutorials of this package will walk you through setting up your run environment and creating a few example programs.

Using this package may not be appropriate if your embedded linux system can run Ubuntu and the full ROS stacks; it is really aimed at smaller or non-x86/Ubuntu linux systems.

Prerequisites

You should have a development toolchain available to you that is capable of compiling C++ and downloading it to your embedded linux system, and know how to use it. Instructions are given for installing and using toolchains for specific platforms, as well as generic procedures that can be adapted to suit all platforms.

Tutorials

Go to the tutorials to learn how to install and use the package to connect your embedded linux system to ROS.

Bugs

Please file new bugs on the project's bug tracker. The bugs listed below are the most serious, which you would want to be aware of when considering use of this technology. You are encouraged to contribute fixes.

1. Service client on the embedded system doesn't work reliably. (Publisher, Subscriber, and Service server are good.) This is true on both arduino and embeddedlinux packages.
2. Parameters are not supported on the embedded system.
3. APIs are not thread-safe